If you've made a mistake by registering a student absent when they are present or vice-versa, you can amend the attendance by following the steps below.
Find the student under the student page. Use the search filter to narrow your search.
Open up the students profile and click on the attendance tab
You'll see the calendar (Month View) under each day, the calendar will show you the students registered attendance. Along with that you will also see a number in smaller font. This number repersent the ID of the attendance.
Click on the small number. This will take you to that particular attendance.
Click on Edit Attendance button and make necessary changes and click on update attendance button.